Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$12.45	13.394%	$14.1176	$14.12	$14.10	$14.10
Purchase #2	$80.60	13.286%	$91.3085	$91.31	$91.30	$91.30
Purchase #3	$233.74	6.730%	$249.4707	$249.47	$249.45	$249.50
Purchase #4	$130.36	11.630%	$145.5209	$145.52	$145.50	$145.50
Purchase #5	$116.27	13.125%	$131.5304	$131.53	$131.55	$131.50
Purchase #6	$146.33	8.700%	$159.0607	$159.06	$159.05	$159.10
Purchase #7	$242.62	3.188%	$250.3547	$250.35	$250.35	$250.40
7 purchase totals =	$962.37		$1,041.3635	$1,041.36	$1,041.30	$1,041.40